1. Field of the Invention
This invention relates in general to subsea well tools, and in particular to a tool that will seal in the bore of a wellhead for testing a blowout preventer located above.
2. Description of the Prior Art
In one type of offshore drilling, a subsea wellhead will be installed at the sea floor. A riser will connect to the wellhead and extend upward to a drilling vessel floating at the surface. A blowout preventer stack will be located within the riser.
It is a good practice to test a blowout preventer by closing the blowout preventer on drill pipe and applying pressure below the drill pipe. This test also tests the seal of the wellhead connector to the subsea wellhead housing. In order to perform this test, the wellhead housing bore needs to be sealed so that the pressure will be applied only from the wellhead housing upward. While test tools are available, improvements are desired.
For example, it would be an advantage to utilize a test tool which locks into internal grooves provided in the wellhead to react against the pressure imposed by the test pressure tending to push the test tool downward. Moreover, it would be desirable to have a test tool that optionally can test without locking into the wellhead grooves within a portion that below the grooves. In that case, the reaction force could be handled by landing the test tool on a casing hanger. Furthermore, it would be desirable to have a test tool which is also capable of being modified for running the wellhead rather than have a completely separate tool for running the wellhead and a separate tool for testing.